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The most accepted method for staining arbuscular mycorrhiza (AM) in vascular plants has been one proposed by Phillips & Hayman in 1970. In particular, for the study of AM in bryophytes (s.l.) [Anthocerotophyta, Bryophyta (s.s.), Marchantiophyta] some authors have introduced modifications to this technique. Even though all these protocols stain AM, their main disadvantage is related to the result of material maceration (e.g. over-softening or completely destroying plant cells due to the high temperatures used, the high concentrations of reagents or the long-term exposure to aggressive chemicals). In order to optimise the results for the observation of AM in this group of plants, a modification is presented to the traditional staining technique. In the protocol here proposed, 70% ethanol is used as fixative and first clarifier, 1% potassium hydroxide (KOH) (80 °C, 20 min) as a second clarifier; 1% hydrochloric acid (HCl) (50 °C, 10 min) as an acidifier and 0.05% trypan blue (60 °C, 20 min) for dyeing. This improved protocol is not destructive, it is fast to perform and it is of wide application since it allows staining the AM in bryophytes.

Anthracene, a polycyclic aromatic hydrocarbon (PAH) from fossil fuel combustion, poses significant environmental threats. This study investigates the role of abscisic acid (ABA) in the anthracene tolerance of the liverwort Marchantia polymorpha using mutants deficient in ABA perception (Mppyl1) or biosynthesis (Mpaba1). In this study, we monitored the role of ABA in the anthracene tolerance response by tracking two ABA-controlled traits: plant growth inhibition and gemmae dormancy. We found that the anthracene-induced inhibition of plant growth is dose-dependent, similar to the growth-inhibiting effect of ABA, but independent of ABA pathways. However, gemmae dormancy was differentially affected by anthracene in ABA-deficient mutants. We found that gemmae from anthracene-exposed WT plants exhibited reduced germination compared to those from mock-treated plants. This suggests that the anthracene exposure of mother plants induces a transgenerational effect, resulting in prolonged dormancy in their asexual propagules. While Mppyl1 gemmae retained a dormancy delay when derived from anthracene-exposed thalli, the ABA biosynthesis mutant Mpaba1 did not display any significant dormancy delay as a consequence of anthracene exposure. These results, together with the strong induction of ABA marker genes upon anthracene treatment, imply that anthracene-induced germination inhibition relies on ABA synthesis in the mother plant, highlighting the critical role of MpABA1 in the tolerance response. These findings reveal a complex interplay between anthracene stress and ABA signaling, where anthracene triggers ABA-mediated responses, influencing reproductive success and highlighting the potential for leveraging genetic and hormonal pathways to enhance plant resilience in contaminated habitats.

Se conoce bien que diferentes sistemas de uso y manejos de suelos afectan la abundancia, la actividad y la composición de la comunidad microbiana del suelo. En este trabajo se estudió el comportamiento de las poblaciones bacterianas cultivables y, en particular, las bacterias solubilizadoras de P (BSP) en muestras de suelo provenientes de un ensayo de larga duración con diferentes secuencias de cultivo. Los resultados obtenidos ponen en evidencia que el desmonte y el uso agrícola posterior luego de 11 años generó una disminución de la población de bacterias cultivables en general, y de las bacterias solubilizadoras de P en particular, con respecto al suelo prístino. Se obtuvieron aislamientos con una alta eficiencia de solubilización de P de los suelos provenientes de las diferentes rotaciones. Estos aislamientos eficientes se clasificaron taxonómicamente mediante análisis 16S RNA como pertenecientes a los géneros Bacillus, Paenibacillus, Pseudomonas y Xanthomonas. En particular, la caracterización de los sobrenadantes de cultivos de los aislamientos Pseudomonas koreensis y Paenibacillus pabuli mostraron que son productoras de ácidos orgánicos. Los ensayos de inoculación combinada de estas dos cepas sobre plantas de maíz en cámara de cultivo pusieron de manifiesto un efecto sinérgico sobre la promoción del crecimiento de esta especie. Los resultados aquí presentados sugieren que si bien las poblaciones de BSP son más numerosas en suelos prístinos, determinadas rotaciones de cultivos a largo plazo favorecen el incremento de bacterias solubilizadoras más eficientes, un aspecto que debería tenerse en cuenta al diseñar futuras estrategias de búsqueda de potenciales bioinoculantes.

The effect of the flavonoids chrysin, isorhamnetin, kaempferol, luteolin, morin and rutin on pre-symbiotic growth, such as spore germination, hyphal length, hyphal branching and the formation of auxiliary cells and secondary spores, of the arbuscular mycorrhizal fungi Gigaspora rosea, G. margarita, Glomus mosseae and G. intraradices was studied. According to the effect on each fungal growth parameter, the tested compounds could be classified to be genus and/or species specific or specific, for a certain developmental stage of pre-symbiotic growth. A clear arbuscular mycorrhizal genus specific, and even species specific, effect of some flavonoids was observed. However, this specificity of a flavonoid could not be generalized but differs depending on the pre-symbiotic stage of the AM fungus. Moreover, our show that for a better understanding of the role of compounds in the AM symbiosis, studies should not be conducted only with one AM fungus looking at one fungal growth parameter such as spore germination or hyphal length, but should be wider, including several growth parameters and several AM fungi. [ABSTRACT FROM AUTHOR]

Se aislaron veintitrés (23) cepas de actinomicetes cultivables de la especie corticícolaPseudocyphellaria berberina presente en la selva templada valdiviana, Argentina, veintún (21) fueronendoliquénicas y dos (2) ectoliquénicas. Se identificaron diecisiete (17) cepas de los géneros Actinoplanes(2), Dactylosporangium (1), aff. Pseudonocardia (1), Micromonospora (6), aff. Micromonospora (1),Streptomyces (5) y Streptosporangoium (1). Este es el primer registro para la Argentina de actinomicetesaislados de hongos liquenizados.